I am presuming the warning messages are there because the mapi versions are not the same? Here are the cdo and mapi version on our servers. Also the warning messages are mainly for the same user, though there are a couple for other users, not many though.

Exchange server 2003 sp2

cdo.dll 6.5.7651.61

Mapi32.dll 6.5.7638.1

BES version 4.1.6.9 running on windows server 2000 sp4

cdo.dll 6.5.7651.61

map32.dll 6.5.6944.0

Which leads me onto my second question how do I go about updating the version of the mapi32.dll file on our windows 2000 server?